Mine firing system



J. F. c0014, 'JR 2,396,914

MINE FIRING SYSTEM 2 Shests-Sheet l OUTPUT CONTROLLER Filed Jan. 15, 1940 QSCI LLATOR OFF O com'AcT AND OBSERVED j I l I I I I I I I I I I l I I I l I I I I l I I I I I I I l I I I I I I I J; F. cooK, JR 2,396,914

MINE FIRING SYSTEM Fi led Jan. 15, 1940 2 Slieets-3heet 2 March 19, 1946 mPreJdomO Patented Mar. 19, 1946 UNITED STATES 9 Claims;

This invention relates to explosive mines, particularly to controlled mines as opposed to the type which are automatically exploded when a ship or other body comes in contact with an externally disposed detonator. It consists in an improved firing system possessing certain advantages in respect to accuracy, convenience and reliability of control as compared to previously known systems. Although the firing system of my invention is advantageous in connection with land mines, it is peculiarly adapted for use with a group of mines of the type used to protect harbors, coastal channels, and other places of strategic importance in the sea, which can be viewed from shore.

A controlled mine system for a group of mines used to protect a harbor for example consists of three parts-a casemate on shore which contains a switchboard and other controlling apparatus, a junction box located on the bottom of the ocean at some distance from shore and containing motors and levers for actuating detonators in the mines, and a group of mines disposed in the neighborhood of the junction box and connected thereto by cables. This general system has proved unsatisfactory and unreliable, chiefly because water enters the junction box and puts the delicate moving parts out of commission. one important object of my invention is to eliminate all moving parts from the junction box of the system and further to employ in the junction box a comparatively small number of parts of standard manufacture, which may be easily replaced.

A further object of my invention is to provide a mine firing system containing a permanent test circuit by means of which the entire system may be tested easily and quickly and without firing any mines.

An important feature of my invention resides in construction which permits any selected mine to be fired according to the desire of an operator in the casemate or to be fired automatically when the mine is canted as the result of being struck by a vessel.

Another important feature of my invention resides in an alarm system by means or which an observer in the casemate is automatically informed when a mine has come in contact with a ship so that he can then proceed to reset the controls and fire the mine at will.

These and other objects and features of my invention will be more readily understood and appreciated from th following detailed description of a preferred embodiment thereof, selected for purposes of illustration and shown in the accompanying drawings in which Fig. l is a schematic diagram of the circuits and elements used in the firing system of my invention.

Fig. 2 is a schematic diagram of the circuits in the casemate.

Although the system of my invention can be used in conjunction with land mines, it is herein illustrated in its application to a group of nineteen sea mines. The illustrated controlling and firing system has three parts-a control station, or casemate,located on shore, a junction boX placed in the water at some distance from the shore, and detonators in each one of the group of mines located in the water beyond the junction box.

In the casemate is a source of alternating current, such as an oscillator ill obtaining its power from any convenient source, or any other type of variable frequency alternator, and designed to operate on a number of different frequencies, each one of which corresponds to the resonant frequency of a tuned circuit disposed respectively in each one of the mines, all as will be more fully described hereinafter.

Assuming that nineteen mines are to be controlled from the one oscillator Ill, the panel of the oscillator is provided with nineteen numbered contacts l2 and a pivotally mounted arm l4 carrying a sliding contact it which can be moved into contact with any selected one of the contacts [2. The arm I l and sliding contact 18 may be replaced by a jack and patching cord arrangement which will afi-ord the selection of a particular frequency without the danger of making an accidental contact which would result in the settin up and transmission of the other frequencies to which other mines in the system may be tuned.

Adjacent the oscillator It] is an output controller l8 which has four contacts on its panel, lettered Off, Test, Delay, and Contact and observed respectively. A pivotally mounted arm 22 is arranged to be moved into contact with any selected contact on the panel to change the voltage of the current coming from the oscillator. A cable 24 leads from the output controller [8 to a distribution box 26 disposed at the bottom of the ocean some distance from the shore. A branch 2'! of the cable leads from a battery 28 or other source of direct current through a switch 29. In

the distribution box 26 the cable 2 1 is connected to the primary of a transformer 38 and to a plurality of choke coils 32 each of which is connected to a transformer secondary coil 34, there being one choke 32 and one secondary coil 34 for each mine in the group. The choke coils 32 are shielded electrostatically and magnetically from the transformer and its circuits. The coils 34 are connected at one side to ground through fuses 36 and blocking condensers 31, and the other end of the coils 34 are connected to cables 38 which lead to the mines to (only one being shown in the drawings). The primary of the transformer 30 is grounded through a blocking condenser 3 I Each mine contains a step up transformer having its primary :4! connected to the cable 38 and to round through a blocking condenser 43. The primary ll and secondary 42 are connected through a choke coil 44. The secondary circuit includes a tuning condenser 46, a blocking condenser Ill, and a detonator 48 arranged to fire the mine. There are several methods of firing the mine, which will be discussed separately. 7

Observed fire By reference to Fig. 2 it will be apparent that when the arm 22 on the output controller I8 is set at Contact and observed, the output of the oscillator is directly connected to the cable 24 to transfer the maximum oscillator output voltage to the transformer 30 in the distribution box 26. The contact 16 has been placed on one of the contacts 12 to give a certain frequency, say 20,000 cycles. The condenser 46 in one of the mines 40 will have been adjustedto cause the secondary circuit in the mine to become resonant at 20,000 cycles so that when the oscillator is delivering 20,000 cycles at the maximum output as determined by the position of the arm 22, high amplitude current will flow in the secondary circuit of the mine 40 to actuate the detonator and fire the mine. Only this one mine will be fired because the tuning condensers in the secondary circuits of the other mines will be tuned to resonance at frequencies other than 20,000 cycles, the circuits being turned Contact fire In the secondary circuit of each mine is a relay 5!), and a switch 52 arranged to close when the mine is tilted as by collision with a vessel. The relay 50 is actuated by direct current from the battery 28, when the switch 29 has been closed, through the cable and choke coils 32 and 44. The necessity for passing direct current through the system accounts for the presence of the choke coils 32 and 44 and also for the blocking condensers 41, 43, 31, and 3|. A blocking condenser 54 is placed in the cable 24 behind the connection of the cable 21. The relay 50 opens the secondary circuit of the mine so that it can be closed only when the switch 52 is closed. Thus the mine can be fired only when it is tilted to close the switch 52 and then only when the oscillator is giving out current at 20,000 cycles, or at the resonant frequency of the tuned circuit in the mine. The battery 28 cannot fire the mine because the detonator 48 is isolated from direct current by the condensers and 41. r

When it is desired to set up the system for contact fire, the arm 22 is set on Contact and observed, the switch 29 is closed, and the oscillator is set to searching continuously and automatically through its frequency band. A searching cycle may be so short that almost immediately after an enemy ship has tilted the mine to close the switch 52, the oscillator will reach the resonant frequency of that mine and the detonation will take place.

Delayed fire connected resistor 62 to the Delay contact on the output controller 18. The resistor 62 is included in parallel in a circuitincluding a rectifier.64, an ammeter 66, a relay 68, and an audible alarm device 69 powered by battery 61. That part of the'resistor 00 in series with the oscillator l0 and the Delay contact on the output controller reduces the effective voltage output of the oscillator so that it is insufiicient to fire the mine but will sound the alarm 69, when the oscillator output coincides with the resonant frequency of a mine and closes the secondary circuit in the mine (without operating the detonator). In this case the circuit is closed when current'at resonant frequency of one of the mines passes to the mine through the cable connections, through the tuned circuit, and back through ground.

In the delayed firefmethod theswitch 29 is closed and the oscillator is set to searching its frequency band. When the mine is tilted the circuit is closed and the reduced current operates the relay 68 to sound the alarm but not to fire the mine. After the alarm has sounded the arm 22 is set to Contact and observed, whereupon the voltage is'stepped up, and the mine is fired when the oscillator neXtreaches the resonant frequency of the tuned circuit in the tilted mine. The delay period may be set at any number of oscillator cycles of searching by merely delaying setting of the output controller to Contact and observed.- 3 '7 I Clearing a mine circuit Aftera mine has been fired, its cableis grounded and it becomes necessary .to disconnect the grounded mine'c'able from the circuit. In order to accomplish this the selector arm 14 is set to the position of the recently-fired mine and the arm 22 is set on Contact and observed? whereupon the grounded and. short circuited mine cable will draw ample current to blow the fuse '36 connected in the circuit of the'fired mine in the distribution box 26.. None of the other mines will be aifected since the ,current' for blowing the fuse is sent out at a frequency which does not coincide with the resonant frequency of thetuned circuit'ofany of the-funfired mines. v

In the foregoing the description of lthe circuits associated with the output controller [8 has been simplified. There are, however, two additional circuits to be considered. In the line from the oscillator tothefContactand observed contact of the output commoners resistor I0 is connected in series and-is placed across the terminals of a second alarmcircuit in which is included a rectifier I2, 'an' ammeter 14, a relay 76, and an alarm signal '18 powered by a battery 19. When the Contact or Observed methods of firing arebeing used, the alarm sounds whenever a mine is-fired. The operator is thus informed that the minefl'ls' fired and that he should proceed as described above to clear the system by blowing a fuse and disconnecting the cable to the fired mine.

From the lower part of the resistor be a line leads through a resistor 80 to the Test contact on the output controller It. The resistor 80 is placed across the terminals of a circuit including a rectifier 82 and an ammeter 84. The lines from the sides of the resistor 86 to the rectifier 82 and the ammeter 64 are connected to the lines leading to the Dale? and Con.- tact and observed contacts on the output controller to a fraction of its maximum voltage, and this reduced voltage is not sufi'icient to fire a mine, although it is sufficient to give a distinctive indication where it may be observed.

When a mine is to be tested, the arm 22 is placed on the Test contact on the output controller It; then the oscillator is set to produce oscillations at the resonant frequency of the tuned circuit of the mine to be tested. If the circuits are all in order, the ammeter 8d will give a certain reading which will be normal. If the resonant circuit is open the reading will be very low. If the resonant circuit is short circuited or grounded or if the firing devic is defective, the current will be greater or less than normal depending upon the nature of the difficulty. The values of the resistors, condensers and coils will largely depend on the frequency range to be used, and the normal values for the test ammeter 84 will have to be found by experience under the conditions of each installation.

It will now be evident that the system of my invention is a Valuable improvement over existing systems which necessitate the employment of many moving parts in the distribution box under water. Furthermore, the presence of the mines is not open to detection by means of apparatus now known. When the observed method of control is used, there is no current fiowing in the system until the contact 16 engages one of the contacts I2 and the arm 22 is set at Contact and observe. Even when this event takes place, there is no current flowing from the distribution box to the mines except that which is instantaneously flowing into the mine which is to be exploded. When the delayed fire method of control is being used, the voltage is considerably reduced and although an electromagnetic field is set up around the cables, its effect would be very slight and could not be detected for more than a few yards. obvious that the mines could not be fired by apparatus on an enemy ship, since the voltage required to fire a mine is much greater than could be transmitted without the use of cables.

Having thus described my invention what I claim as new and desire to secure by Letters Patent of the United States is:

1. A firing system for a controlled mine, which comprises a detonator in the mine, a tuned circuit in the mine controlling the detonator, a distribution box, a transformer disposed in the distribution box, a choke coil connected across the transformer, a relay in the mine for opening the tuned circuit, a tilting switch included in the tuned circuit when the relay is energized, a transformer in the mine having its secondary included in the tuned circuit, a choke coil connected across the transformer in the mine, a cable connecting the primary of the mine transformer to the secondary of the transformer in the distribution box, an oscillator arranged to transmit current at the resonant frequency of the tuned circuit in the mine, an output controller connected to the osciltil lator and the primary of the transformer in the distribution box, a source of direct current connected to the primary of the transformer in the distribution box, and a switch for turning the direct current oil or on, whereby the relay in the mine may be energized by direct current to maintain the tuned circuit open until the tilting switch closes.

.2. A firing system for controlled mines, which comprises a differently tuned circuit in each mine, a detonator included in each tuned circuit, an oscillator arranged to transmit current at selected frequencies, and separate cable connections between the respective mines and the oscillator, whereby one mine may be fired without affecting the others in a group.

3. A firing system for a group of controlled mines, which comprises, a detonator in each mine,

' a tuned circuit in each mine for operating the Itis.

detonator, a distribution box, a transformer in said distribution box, a plurality of secondary coils forming part of said transformer each secondary coil being connected to a tuned circuit in one of the mines, a source of alternating current of controlled frequency connected to the pri mary of said transformer, means for changing the voltage of the alternating current, and a circuit including an ammeter so connected t the voltage changing means that the ammeter circuit is only closed when the current is at minimum voltage.

4. A firing system for a group of controlled mines, which comprises a tuned circuit in each mine, each circuit having a different resonant frequency, a detonator included in each tuned circuit, a step up transformer disposed in each mine and having its secondary included in the tuned circuit, a casing, a step-down transformer in said casing, a plurality of secondary coils in said casing, cables connecting said secondary coils to the primaries of the transformers in the mines, a source of alternating current remote from the casing and the mines, an output controller connected to said source of current and to the primary of the transformer in the casing, means for selecting the frequency of the alternating current, a source of low voltage direct current, a tilting contact switch in each mine, a relay in each mine connected to said direct current source and operating to break the tuned circuit until the mine is canted to close the tilting contact switch, and means for automatically varying the frequency of the alternating current through a predetermined range corresponding to the resonant frequencies of the tuned circuits, whereby a selected mine may be fired by opening the direct current circuit and transmitting alternating current at the resonant frequency of the tuned circuit in the mine and whereby the mines may be set to explode when canted by closing the direct current circuit and transmitting alternating current at automatically varied frequencies until the transmitted current reaches the resonant frequency of a mine which is canted.

5. A firing system for a group of mines, which comprises an oscillator capable of searching automatically through a predetermined range of frequencies, a tuned circuit in each mine, each circuit being tuned to a different resonant frequency, a voltage controller connected to said oscillator and to each tuned circuit, an alarm connected to said voltage controller and operable when the voltage is relatively low, a tilting switch included in each tuned circuit, a detonator also included in each tuned circuit and operable only on a relaoperated when the voltage is relatively 'low, the mine is canted to close the tilting switch, and the oscillator is transmitting at the resonant fre quency of the tuned circuit in the canted mine; whereupon the voltage may be increased to' fire the mine. 7

6. A firing system for a group of controlled mines, which comprises, a detonator in each mine, a different tuned circuit connected to each detonator, an oscillator arranged to transmit current at selected frequencies with sufilcient voltage to operate said detonators, an ammeter, and means I for reducing the voltage output of the oscillator to a value insumcient to operate a detonator and alarm and said ammeter to the output circuit of the source of alternating current, whereby the alarm is connected in the circuit when relatively 7 tively high voltage current, whereby the alarm is 8; A firing system for mines; which comprises, a source of alternating current, a tuned circuit in the mine, a detonator included in the tuned circuit, a tilting switch' also included in the tuned circuit, an output controller for the source of alternating current connected to said source and to said tuned circuit and adjustable to provide either relatively low output voltage insuificient to operate the detonator or relatively high output voltage capable of operating the detonator, an alarm connected to said output controller and operable on either high or low voltage, whereby said system may be operated on relatively low voltage until the tilting switch is closed and. the alarm sounds, whereupon the voltage may be increased to operate the detonator.

,9. A'mine firing system, which comprises a group of mines, a differently tuned circuit in each mine, a detonator included in each tuned circuit, a distribution box having an electrical connection to each mine and means for varying the voltage of the current transmitted through said connection, an oscillator, a cable connecting the distribution box to the oscillator, and Vfuses in said distribution box connected in the leads to the individual mines whereby the oscillator may be operated at the resonant frequency of an of the tuned circuits to fire the selected mine or operated to transmit current at increased voltage to blow the fuse in the circuit of the fired mine to clear the system from the fired mine.

JOSEPH F. COOK, JR. 

